1. Field of the Invention
This invention relates generally to measurement and data acquisition systems and, more particularly, to a data acquisition system with an improved integrated digitizer having a streaming interface.
2. Description of the Related Art
Measurement systems are oftentimes used to perform a variety of functions, including measurement of a physical phenomena, measurement of certain characteristics or operating parameters of a unit under test (UUT) or device under test (DUT), testing and analysis of physical phenomena, process monitoring and control, control of mechanical or electrical machinery, data logging, laboratory research, and analytical chemistry, to name a few examples.
A typical contemporary measurement system comprises a computer system, which commonly features a measurement device, or measurement hardware. The measurement device may be a computer-based instrument, a data acquisition device or board, a programmable logic device (PLD), an actuator, or other type of device for acquiring or generating data. The measurement device may be a card or board plugged into one of the I/O slots of the computer system, or a card or board plugged into a chassis, or an external device. For example, in a common measurement system configuration, the measurement hardware is coupled to the computer system through a PCI bus, PXI (PCI extensions for Instrumentation) bus, a USB (Universal Serial Bus), a GPIB (General-Purpose Interface Bus), a VXI (VME extensions for Instrumentation) bus, a serial port, parallel port, or Ethernet port of the computer system. Optionally, the measurement system includes signal-conditioning devices, which receive field signals and condition the signals to be acquired.
A measurement system may typically include transducers, sensors, or other detecting means for providing “field” electrical signals representing a process, physical phenomena, equipment being monitored or measured, etc. The field signals are provided to the measurement hardware. In addition, a measurement system may also typically include actuators for generating output signals for stimulating a DUT or for influencing the system being controlled. These measurement systems, which can be generally referred to as data acquisition systems (DAQs), are primarily used for converting a physical phenomenon (such as temperature or pressure) into an electrical signal and measuring the signal in order to extract information. PC-based measurement and DAQs and plug-in boards are used in a wide range of applications in the laboratory, in the field, and on the manufacturing plant floor, among others.
Multifunction DAQ devices typically include digital I/O capabilities in addition to the analog capabilities described above. Digital I/O applications may include monitoring and control applications, video testing, chip verification, and pattern recognition, among others. DAQ devices may include one or more general-purpose, bidirectional digital I/O lines to transmit and receive digital signals to implement one or more digital I/O applications. DAQ devices may also include a Source-Measure Unit (SMU), which may apply a voltage to a DUT and measure the resulting current, or may apply a current to the DUT and measure the resulting voltage.
Typically, in a measurement or data acquisition process, analog signals are received by a digitizer system, which may reside in a DAQ device or instrumentation device. A digitizer system is a device that uses one or more Analog to Digital Converters (ADC) in order to capture segments of interest of a time varying analog electric signal as a digital representation to be stored and processed by a computer system. There are several important design tradeoffs to be considered when implementing digitizer systems, depending of which components of the system can be included on the same integrated circuit (an integrated circuit can be a custom circuit, such as an application specific integrated circuit [ASIC], or a field programmable gate array [FGPA], among others).
There are presently many different implementations of digitizer systems and streaming interfaces for these systems. One common arrangement includes modular ADCs and integrated complete digitizer systems because the technology process required for the high speed ADCs is usually not the optimal process for the logic required for the other components of the system. Modular ADCs were the motivation behind the specification JESD408, which describes a protocol to transmit data serially between these two components. While designed for high-speed data, the specification is designed to support a continuous stream of data, as generated by the ADC, and lacks a mechanism to define records of data to be stored by the memory system. Current digitizers are typically designed to capture records of data of interest into internal integrated or modular memory.
Other corresponding issues related to the prior art will become apparent to one skilled in the art after comparing such prior art with the present invention as described herein.